The documents listed below are incorporated herein by reference and are referred to hereinafter by their corresponding identification numerals show below enclosed in square brackets.
[1] IEEE 802.11 Working Group, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications,” 1997.
[2] J. Monks, V. Bharghavan, W. Hwu, “A Power Controlled Multiple Access Protocol for Wireless Packet Networks,” in IEEE INFOCOM, April 2001.
[3] A. Nasipuri, S. Ye, J. You and R. Hiromoto, “A MAC Protocol for Mobile Ad Hoc Networks using Directional Antennas,” in IEEE Wireless Communications and Networking Conference (WCNC), Chicago, Ill., September 2000.
[4] R. Roy Choudhury, X. Yang, R. Ramanathan and N. H. Vaidya, “Using Directional Antennas for Medium Access Control in Ad Hoc Networks,” in ACM MOBICOM, Atlanta, Ga., September 2002.
[5] Y.-B. Ko, V. Shankarkumar and N. H. Vaidya, “Medium Access Protocols using Directional Antennas in Ad Hoc Networks,” in IEEE INFOCOM, March 2000.
[6] A. Nasipuri and S. R. Das, “Multichannel CSMA with Signal Power-based Channel Selection for Multihop Wireless Networks,” in IEEE Vehicular Technology Conference (VTC), September. 2000.
[7] A. Nasipuri, J. Zhuang and S. R. Das, “A Multichannel CSMA MAC Protocol for Multihop Wireless Networks,” in IEEE Wireless Communications and Networking Conference (WCNC), September. 1999.
[8] N. Jain and S. Das, “A Multichannel CSMA MAC Protocol with Receiver-Based Channel Selection for Multihop Wireless Networks,” in Proceedings of the 9th Int. Conf. on Computer Communications and Networks (IC3N), October 2001.
[9] S.-L. Wu, C.-Y. Lin, Y.-C. Tseng and J.-P. Sheu, “A New Multi-Channel MAC Protocol with On-Demand Channel Assignment for Multi-Hop Mobile Ad Hoc Networks,” in IEEE Wire-less Communications and Networking Conference (WCNC), Chicago, Ill., September 2000.
[10] W. Hung, K. Law and A. Leon-Garcia, “A Dynamic Multi-Channel MAC for Ad Hoc LAN,” in 21st Biennial Symposium on Communications, April 2002.
[11] IEEE 802.11a Working Group, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications—Amendment 1: High-speed Physical Layer in the 5 GHz band,” 1999.
[12] J. Stine, “Energy Conserving Protocols for Wireless Data Networks,” Ph.D. dissertation, University of Texas at Austin, 2001.
[13] J. Stine, G. de Veciana, K. Grace, and R. Durst, “Orchestrating Spatial Reuse in Wireless Ad Hoc Networks using Synchronous Collision Resolution,” Journal of Interconnection Networks, Vol. 3 No. 3 & 4, September and December 2002, pp. 167-195.
[14] ETSI, EN300 652 V 1.2.1, “Broadband Radio Access Networks (BRAN); High Performance Radio Local Area Network (HIPERLAN) Type 1; Functional Specification, July 1998.
[15] J. Stine and G. de Veciana, “A Comprehensive Energy Conservation Solution for Mobile Ad Hoc Networks,” IEEE International Conference on Communications, 2002.
[16] J. Stine, B. Durst, and K. Grace, “Methods to Achieve Capacity and Quality of Service in Ad Hoc Networks,” Proceedings of the Army Science Conference, 2002.
[17] K. Grace, “SUMA—The Synchronous Unscheduled Multiple Access Protocol For Mobile Ad Hoc Networks” Proceedings Eleventh International Conference on Computer Communications and Networks, IC3N'2002, October 2002.
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Ad hoc networks have been proposed as a solution to wireless networking where nodes are mobile, the range of their mobility exceeds the transmission range of any single transceiver, and there is no existing network infrastructure. Mobile Ad hoc networks (MANET) have a widespread application ranging from military to consumer devices. The following are some of the applications that are useful for MANETs.
MANETs can be used to extend the coverage of wireless LAN by their integration and interoperation with infrastructure network. MANETs have their widespread use in covering blind spots in cellular networks and they can also be used to extend the coverage of cellular networks.
MANETs can also be used for personal area networks, which can be used to build smart home network formed by commercial appliances.
Sensor networks are the group of smart, inexpensive devices with multiple sensors to provide opportunities for enabling, monitoring and controlling target systems. Such sensor nodes have capability for acquiring and embedded processing of variety of data forms. Collaborative signal processing and fusion algorithms are needed to aggregate the distributed data from among the nodes in the network, including possibly multiple modalities of data within a sensor node, to make decisions in a reliable and efficient manner.
MANETs also find their use in establishing ad hoc wireless communication to carry out search and rescue operations, as the infrastructure wireless network is not present.
On military battlefields, there is typically no infrastructure present for wireless communication. Hence MANETs are extensively used by military for communication purposes.
An ad hoc network is a collection of wireless mobile nodes dynamically forming a temporary network without using the existing network infrastructure or centralized administration. Due to limited transmission range of wireless network interfaces, multiple network hops may be needed for nodes to exchange data with each other across the network. The applications of ad hoc networks are far reaching from supporting 3G technologies, consumer devices to military communications. The current demands of wireless communications and the apparent scarcity of the spectrum to support them requires that there be communication schemes that enable the dynamic reuse of spectrum to support multiple users, as they need it. Ad hoc networking is the proposed paradigm to solve the problem.
The IEEE 802.11 standard for wireless LAN [1] has a medium access control (MAC) protocol designed for sharing a single channel between hosts. Due to the broadcast nature of wireless transmission, when two hosts are communicating, all other hosts within the range of the two hosts must defer their communication in order to avoid collision. IEEE 802.11 suffers from significant throughput degradation as the number of active hosts increases. It also suffers from hidden terminal and exposed terminal problem and is also not fair. A lot of work has been done to improve the throughput of wireless networks, and various approaches have been proposed. One approach is to control the transmission power [2]. The basic idea of power control is to have the sender transmit with power just enough to reach the target node, so that the space blocked by that particular transmission is minimized. Another approach is to use directional antennas instead of omni-directional antennas [3], [4], [5]. Directional antennas are able to transmit signal in one direction, so that the hosts located in other directions can communicate concurrently without interfering with each other. These two approaches improve the throughput by increasing spatial reuse, but still they use only a single channel.
Data transmitted in different channels do not interfere with each other, and thus can take place in the same region simultaneously. So the throughput can increase significantly, proportional to the number of channels in the ideal case. Also having multiple channels can provide further benefits in addition to increased throughput, such as a more simple way to support QOS.
The IEEE 802.11 standard already has multiple channels available for use. Table I summarizes the features of IEEE 802.11.
TABLE IFEATURES OF IEEE 802.11 STANDARDS802.11b802.11aPhysical LayerDSSS1OFDM2Maximum Speed11Mbps54MbpsFrequency Band2.4GHz5GHzNumber of Channels38/431Direct Sequence Spread Spectrum2Orthogonal Frequency Division Multiplexing38 for indoor use, 4 for outdoor use.
IEEE 802.11b physical layer (PHY) has 14 channels, 5 MHz apart in frequency [1]. But to be totally non-overlapping and thus feasible for use in the same region, the frequency spacing must be at least 30 MHz. So channels 1, 6 and 11 are typically used for communication in current implementations, and thus we have 3 channels available for use. IEEE 802.11a provides 12 channels, 8 in the low part of the band for indoor use and 4 in the upper part for outdoor use [11]. There is enough motivation for concurrent use of multiple channels, but the current MAC protocol of IEEE 802.11 is designed for sharing a single channel. The main reason for this is that each IEEE 802.11 host is equipped with one half-duplex transceiver, so it can only transmit or listen on one channel at a time. So when a host is listening on a particular channel, it cannot hear the communication taking place on a different channel. Due to this, as observed in [9], if a single-channel MAC protocol (such as IEEE 802.11 DCF) is applied in a multi-channel environment wherein each node may dynamically switch channels, performance degradation may occur (unless additional precautions are taken to manage dynamic channel selection).
The present invention recognizes that it is desirable to a provide multi-channel MAC protocol for wireless mobile ad hoc networks that is capable of utilizing multiple data channels simultaneously.